Generally, an information processing apparatus including an existing computer involves employing a hard disc device as an information storage medium.
The hard disc device is the most standard type of data storage device in a computer system. The hard disc device is stored with operating system (OS) and application programs. Further, the hard disc device is stored with user data and operation data. A 3.5-in. type hard disc device, which is a mainstream type of device at the present, has a storage capacity that is equal to or larger than 100 gigabytes per device.
The hard disc device magnetically records the data by rotating at a high speed a disc (also called a [platter]) constructed of a glass or aluminum circular plate coated or vapor-deposited with a magnetic substance. A multiplicity of tracks are disposed concentrically on this platter. Further, sectors (a sector is a unit for reading and writing the data, and one sector normally consists of 512 bytes through several kilobytes) are regularly arranged within the track.
In the hard disc device, when reading and writing the data, at first, a head slider (which will hereinafter be referred to as a head portion) including a read/write head is moved onto a target track. Note that the movement of this head portion is called a ‘seek’. After the seek, the hard disc device, when the head is moved to a position just under the target sector, starts reading and writing the data. Total time of a period of seek waiting time and a period of rotation waiting time becomes a period of access time (a period of time till a data transfer is started) to the hard disc. This access time to the hard disc device generally requires several milliseconds. Then, once the data transfer is started, a data transfer speed of the hard disc device is determined corresponding to a rotating speed and a record density of the platter.
Note that in the hard disc device, the head can access a plurality of tracks existing in the same position through one seek by using double sides of the single platter or by simultaneously employing a plurality of platters. Accordingly, performance of the hard disc device is improved by such methods. By the way, in the hard disc device, according to the methods such as erasing the data or formatting (initializing) the disc, etc., the stored data simply look disappeared from the computer.
Namely, the data erasing method given above is a method of deleting, e.g., connection information (initial entry) among blocks configuring a file. In this method, though the connection information among the blocks is deleted, the blocks for storing the data still remain undeleted. Further, the data erasing method described above, for instance, intends to make the data unable to be read by writing the same information (Ex.: 0) to all the files. This method has a possibility that the original data might be decoded by a difference from the same written information.
The hard disc device with the data appearing as if erased can be read if using a special piece of software. Hence, unless a proper measure is taken for the data in the hard disc device in case of disposal or a transfer of a personal computer, a malicious third party might reuse the data of the previous user.
Therefore, when discarding the hard disc device described above, the data can not be completely erased unless the disc medium (storage medium) is destroyed by deassembling the hard disc device.
Accordingly, the general user, inconveniently enough, must destroy the hard disc device by deassembling the computer when discarding the computer. Moreover, even when a waste disposal company conducts a discarding treatment of the computer, this treatment involves a manual work, and consequently it is not so easy to discard a tremendous quantity of hard disc devices. A problem arising when discarding the storage medium is the same with other types of storage mediums such as a CD (Compact Disc), a (DVD (Digital Video or Digital Versatile Disc), an MD (Mini Disc), an FD (Flexible Disk) and so on.
By the way, a technology (refer to, e.g., Patent document 1) for destroying, e.g., an optical disc is disclosed as a technology for destroying the storage medium.
Patent Document 1
Japanese Patent Application Laid-Open Publication No. 64-30024